Field of the Invention
This invention relates to improvements in intraocular lenses suitable for use as artificial lens implants and to a method for securing the lens within either of the anterior or posterior chamber of the human eye.
The natural crystalline lens in man is an optically clear organ situated behind the pupillary aperture of the eye. The function of this lens is to help form a sharp image on the retina to provide for acuity of vision. In certain circumstances opacity may develop in the lens, necessitating the surgical extraction of the natural lens from the eye. The condition of lens opacity is called cataract. The absence of the crystalline lens from the eye is known by the term aphakia. After the extraction of the lens, the eye is defective from an optical point of view due to the loss of diffraction of the lens, which should be corrected with optical aids. The optical correction of this connection is called aphakic correction.
The implantation of an artificial intraocular lens is a surgical technique which in recent years has come into increasing use for the correction of aphakia. It will be understood that with the implanting of an artificial intraocular lens in either of the anterior or posterior chambers of the human eye to replace the natural crystalline lens of the eye, severe demands are made on positioning and maintaining the artificial lens fixed within the desired eye chamber.
Accordingly, a vastly increasing number of designs of intraocular lenses are being made available in order to improve the ease at which surgical implantation of the lens can be performed and to provide more exact and assured fixation of the lens in the eye. Most of the available intraocular lenses include lobes or position fixation elements which are in the form of two or more loops. In some lenses, anteriorly as well as posteriorly mounted loops are provided. The fixation loops extend generally radially of the plano-convex lens body and are spaced from one another generally at opposite positions around the periphery of the lens body and are substantially disposed in a common plane with the plano-convex lens. Recently, the fixation elements for artificial lenses have been made unitary with the lens body such that they are not separately attached elements but are formed with the lens body by molding or machining or the like, a single block of any suitable physiologically inert and nontoxic synthetic resin such as are well known to the art, e.g. polymethylmethacrylate.
As stated above, lens implantations are not only extremely difficult and delicate operations, but the use of currently available intraocular lenses, even by a highly skilled surgeon, entails a number of disadvantages. One disadvantage is that available lenses are somewhat difficult to manipulate, given the relatively limited environment within which the surgical implantation is accomplished. As a result, improper fixation of the lens can easily occur, which often makes it necessary for the surgeon to go back into the eye within a few days after the initial implantation in order to correct the positioning error. Another disadvantage is that the lenses are often not provided with suture fixation capabilities. While some surgeons to not feel the necessity of suture fixation, there are times when suture fixation can greatly aid in the process of implanting the intraocular lens as well as provide assured fixation of the lens within the eye chamber. For example, dislocation of the implanted lens is averted, whether from side-to-side or down into the vitreous through ruptured zonules. With superior limb fixation, there is no propeller effect from lenses that may not be of the proper size. Further, during experiences of a traumatic iris prolapse superiorly which could be excised the lens will be securely held by a suture in spite of the absence of the iris at the superior position. Still another disadvantage of available lenses derives from the need to manipulate surgical instrumentation within the eye during implantation and positioning, requiring extremely delicate surgical techniques.
Typical of relatively recent intraocular lens structures which have been patented include U.S. Pat. Nos. 4,174,543, issued Nov. 20, 1979 to Kelman, which discloses an anterior chamber lens provided with four point position fixation formed substantially from a pair of laterally extending and deflectable fixation elements, no suture capacity being provided; 4,092,743, issued June 6, 1978, also to Kelman, which comprises an intraocular lens provided with two lateral position fixation elements, the dimensions as well as the structure of the fixation elements are such that the lens can be snaked through a corneo-scleral incision which can be made only slightly longer than the diameter of the lens body, the superior limb fixation element being provided with a suture hole; and 4,110,848, issued Sept. 5, 1978 to Jensen which discloses an intraocular lens for implantation into the posterior chamber of the eye in which the lower fixation loop has a notch which is disposed between the peripheral edge of the plano-convex lens body and the end portion of the loop so that a suture can temporarily secure the lens to the iris of the eye, the fixation loops are mechanically coupled to the peripheral edge of plano-convex lens and may be formed of the same material as the lens body.